Federal Department of Home Affairs FDHAFederal Office of Meteorology and Climatology Mete oSwiss

Next generation radar precipitation measurement in the Swiss Alps: strategy and first results

Urs Germann, MeteoSwiss, Locarno-MontiM Gabella, L Panziera, M Sartori, I Sideris, M Boscacci, A Hering, L Clementi, M Sassi

Design of new Swiss radar networkis driven by experience, new technology and applications .

2006-2011 (6y)

2Next generation QPE in the Swiss Alps, Urs Germann

Maggia river in Solduno926 km2, southern SwitzerlandTough from radar point of view (heavily shielded, strong clutter, and persistent orographic rainfall)

Typical runoff: 10 m3/sAbout once in a year: >1000 m3/s

2006-2011 (6y)

Select eventswith 16 highestrunoff.

Make 2 groups: • 8 heaviest• rank 9-16

Total rainfall

(sum overall events)

rank 9-168 heaviest

mm50 1800

mm50 1800

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mm mm

Contributionof

convectivecells

%%10 90 10 9050 50

CFAD: Contour frequency altitude diagram 8 heaviest rank 9-16

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Panziera et al, in preparation

High resolution in vertical dimension� to understand orographic precipitation

(combining Doppler and polarimetry)� to determine the VPR� to estimate precipitation at ground in shielded

regions � to reduce stochastic part of QPE processing

(VPR, partial shielding, Z-R, …)

Scan strategy

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Full scan in short time� 20 sweeps in 5 min to properly sample the

vertical dimension + thunderstorm evolution� 10 + 10 interleaved sweeps to obtain

pseudo 2.5min resolution� “oversampling” at low angles to improve QPE

Hei

ght

up to18 km

old 3rd generation

20 sweeps every 5 minutes

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Hei

ght

0 km

Distance from antenna0km up to

246km

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Dedicated nowcasting systembased on radar/raingauge/modelto predict debris flow risk atlocation of gas pipeline

Poster by L Clementi (93 NOW)

Dedicated nowcasting systembased on radar/raingauge/modelto predict debris flow risk atlocation of industry/highway

System designReal-time availability�Products ready on server <1 min after scan�Products updated every 2.5 min

combining latest 2 half-scans (to be refined)

Clutter � all moments at 83 m radial resolution

transferred to central server� add polarimetry for clutter removal (to be done)

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� add polarimetry for clutter removal (to be done)

� short pulse-length of 0.5 mus (83m resolution)

(…)

3 radars replaced by completely newPolarimetric Doppler C-band systemswith ROEL design

Start construction of 2 additional radar

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2 additional radar stations in the inneralpine regions

5 identical systems

Test equipment• ZDR: 0.67 dB bias (Rx H, Tx 135°)

In agreement with: drizzle 0.8; sun 0.8

• rhoHV (Rx H, Tx 135°)• pulse shape• scan strategy• cross-pol isolation• beamwidth and side lobes in H, V behind radome

Cimetta1645 m.a.s.l.

10Next generation QPE in the Swiss Alps, Urs Germann18 km

M Gabella, M Sartori, in collaboration with armasuisse

Receiver

Transponder

Lema radar1625 m.a.s.l.

Sun: monitoring Rx and antenna pointingNoise source: continuous automatic calibration

11Next generation QPE in the Swiss Alps, Urs GermannFollowing I Hollemann et al

M Gabella, M Boscacci

Very 1 st image of new Lema radar

100 km

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AlbisLosses (Tx, Rx, Radome, NF):

old: 14.5 dBnew: 4.9 dB

Transmitted power: old: 270 kWnew: 235 kW per channel (loosing 0.6 dB)

Higher sensitivity

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9 dB more sensitivity thanks to - moving transmitter on tower, - using digital receiver technology, and- moving receiver on the antenna (ROEL)

Zh83mgates

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QPE

dBZ40 55250

Zh83mgates

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QPE

dBZ550 4025

QPE design

�Use all sweeps and radars above a ground pixel in a weighted manner

�Go directly from multi-radar high resolution polar data to surface QPE(i.e. no CAPPI, no single-radar QPE)

�Start with single polarisation

Polarimetry

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�Design algorithm such that QPE converges to single-pol QPE in caseof failure of polarimetry

�Watch out for contamination ofpolarimetry by side lobe clutter

�Remind that in the Alps the lowestradar measurements are often in themelting layer or above

Tentative steps with polarimetry: R(KDP)

raingauge

15-16 UTCGauge 44 mmZh 13 mmKDP 40 mm

7 July 2011, 1525 UTC

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raingaugeLugano @ 10.7 km/111.3°

83 m gates

Dual-Polarisation Weather Radar Handbook, Bringi et al., 2007

R Notarpietro, M Gabella

Real-time radar-raingauge merging

Universal co-krigingRadar-only QPE

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-0.8 Bias/dB (best is 0.0) -0.082.7 SCATTER/dB (best is 0.0) 2.2

(evaluated at hourly scale, pooling 12 representative events)See also:

Talk 3A.6: I Sideris et alTalk 3A.4: R Erdin et al

Poster 20: D Keller et al

Thank you

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1st generation 1961 4th generation 2012

Don’t sacrifice the vertical resolutiondBZ

25

40

55

mm/h

1

10

100

last

60km40200-20-40

Full volume: 20 elevations every 5min

Hei

ght A

SL

[km

]

12

0

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13

25

0.2

1

Lowest 4 every 5min, full 9 every 15min

East-west distance [km] 60km40200-20-40

Hei

ght A

SL

[km

]

12

0

East-west distance [km] 60km40200-20-40

Improve inneralpine coverage

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Inneralpine coverage and backup

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